The Research Of Extracting Metal Ions By Supercritical Carbon Dioxide Fluid

Supercritical Fluid Extraction (SFE) is a new kind of separation technology. As a promising process of extractive separation, it is very significant to study on SFE in view of favorable of applied prospect. In recent years, a great deal of investigations on the theory and the application, especially on the application in the environmental protection.Supercritical carbon dioxide (SC-CO₂) has been most frequently used as a solvent in supercritical fluid extraction, because of CO₂ has low critical temperature and pressure (T_c=304.1K, p_c=7.38MPa), low toxicity and chemical inertness. So supercritical carbon dioxide extraction technology attracted more and more attention, and has been used in many fields. When supercritical carbon dioxide extraction technology used in the envorinmental protection, it found a new way to deal with the heavy metal ions pollution.Because of carbon dioxide is non-polar, it is difficult to extract polar and ionic analytes. There are three ways have reported used to facilitate the SFE of metal ions. The first is increasing the polarity of the carbon dioxide by additon modifer; the second way is converting metal ions into neutral metal complex; the thired way is using the carbon dioxide microemulsions.In this paper, ethanol was used as modifer to increase the polarity of the supercritical carbon dioxide. We studied the effects of pressure, temperature, modifers and extracted time on extraction of metal ion Cu²⁺, Ni²⁺ and Co²⁺ by supercritical carbon dioxide.In this paper, we also used the carbon dioxide microemulsions to extract the metal ions .The carbon dioxide microemulsions formed by surfactant Triton X-100.Experimental results show that the way by use ethanol as modifer to increase the polarity of the supercritical carbon dioxide is a usefull way to extract the above ions.